X-ray apparatus



June 20, 1939. 'BQUWERS ET AL I 2,162,833

X-RAY APPARATUS Filed July 17, 1931 LVBOfO/J.

Patented June 20, 1939 PATENT OFFICE 2,162,833 X-RAY APPARATUS Albert Bouwers and Alfred Kuntke, Eindhoven,

Netherlands, assignors to N. V. Philips Gloeilampenfabrieken, Eindhoven, Netherlands Application July 17, 1931, Serial No. 551,516 In the Netherlands July 17, 1930 3 Claims. (c1. 250-98) This invention relates to an X-ray installation adapted for making instantaneous exposures. It is well known to use for this purpose a condenser which after being charged up to a given voltage is discharged through an X-ray tube, so that a current of high intensity but of short duration is caused to pass through the tube.

According to the invention, an installation of this kind comprises an inductance connected in series with a condenser. The term condenser as used'he'rein is intended to include a group of condenser elements, for example a battery of Leyden jars. It is found that thus better results are obtained which may be accounted for by a more favourable variation of the current and voltages of the, X-ray tube.

An important advantage incidental to the use of an inductance according to the invention is that the condenser can have a lower capacity and the energy required is usedmore efiiciently.

It is not always necessary that a distinct inductance should be included in the circuit, but often the transformer winding which supplies the charging current of the condenser may be used for such inductance. For this purpose a circuit device may be provided, but even the latter may be dispensed with, if the X-ray tube in series with a spark gap is connected in parallel with the rectifier through which the condenser is charged. If in this case the primary circuit of the transformer remains closed, the X-ray tube is acted upon by the sum of the voltages of the transformer winding and of the charged condenser. It may be important that it be possible to obtain a lower voltage. This may be effected with this circuit arrangement by means of a second spark gap bridging the former gap and the transformer winding, and by making the arrangement such that the former or the latter spark gap can be caused at will to become operative.

In order that the invention may be more clearly understood and readily carried into effect two embodiments of the invention will now be described more fully'with reference to the accom panying drawing, in which:

Figure 1 is a diagram showing the variation of the voltage across an X-ray tube with or without the utilisation of an inductance.

Figures 2 and. 3 are schematic diagrams of X-ray installations according to the invention.

Referring to Figure 2, an X-ray tube I receives its anode current from a condenser 2 which is charged by a transformer 3 through a rectifier 4. For the sake of clearness the circuits of the cluded in the circuit.

incandescent cathodes of the X-ray tube and of the rectifier are omitted. The rectifier may be made up of one or more discharge tubes, but also may consist of one or more rectifiers of a different type. 5

The X-ray tube has mounted in series with it a spark gap 5. Once the condenser becomes charged up to a given voltage, a break-down of the spark gap occurs and the condenser is discharged through the X-ray tube so that an instantaneous exposure is obtained.

Reference numeral 6 designates an inductance which in accordance with the invention is in- The importance of this inductance may be clearly understood by refer- 16 once to Figure 1 in which the curve 1 represents the variation of the voltage across the X-ray tube as a function of time, if the inductance 6 is not present. In order to permit the passage of a given efiicient energy through the tube, the con- 2 denser must become charged up to a voltage of e1. At this voltage the action of the discharge is, however, not yet fully efiicient, since the voltage is too high to produce rays giving a sufiicient contrast effect. Only after the voltage has fallen to 5 the value e2, have the rays lost enough of their hardness to be able to produce a clear radiographic image. Below the value es, the rays become too soft and an efficient action no longer occurs. During the time interval between t2 and t3, the discharge is consequently efi'iciently used.

From to till 152 no particularly useful radiation occurs but during this time a very large part of the energy available is consumed as in this case the voltage, and consequently the current intensity, are high. By including in the circuit a choke coil 6, the variation of the voltage becomes approximately as indicated by the line 8. In this case the voltage rises rather quickly from zero to the value eg Where the occurrence of useful 40 X-rays begins. The voltage conserves a value in the useful region from the moment t4 till t5 and then falls again below the value e3.

Clearly, in the second case the energy of the condenser discharge is utilized almost entirely at a favorable voltage. Consequently, less energy sufficies and the condenser may have a smaller capacity. The two cases are such that the time during which the voltage has a suitable 0 value is equal. This may be controlled not only by the value of the capacity but also by the value of the inductance. If, for example, a capacity of 0.6 microfarad is used, a favourable result is found to be obtained by means of an inductance having a value of about 1000 henries. However, as a rule, much smaller capacities sufiice.

Figure 3 shows a circuit diagram of an installation in which the transformer winding which supplies the charging current of the condenser also acts as an inductance in the discharge circuit. In this case, the condenser 9 is charged through the rectifier 12 by a transformer having a low voltage primary winding I and a high voltage secondary winding H. The rectifier has connected in parallel with it an X-ray tube [3 and a spark gap connected in series with the latter and having electrodes M and [5. If a discharge occurs between these electrodes, the current flows from the condenser 9 via the winding I l and the spark gap through the X-ray tube.

The condenser may be discharged while the primary circuit of the transformer remains closed. In this case the X-ray tube is acted upon in addition by the voltage induced in the winding H. A second spark gap may, however, be provided so as to ensure that the voltage of the condenser alone is active. This purpose is served by the connection which leads from the end of the winding II which is connected to the condenser to a spark gap electrode l6. Thus, the electrodes I 3 and I6 have formed between them a spark gap bridging the winding H and the spark gap between [4 and [5. The electrode l4 may, for example, be movable so as to be adapted to be moved at will in the direction of i5 or in the direction of !6 so that either the former or the latter spark gap is caused to be operative when the condenser voltage reaches a sufficiently high value so that a discharge occurs acrosss one of said gaps. Causing one or the other spark gap tobecome operative at will, may of course, be rendered possible in a difierent manner without departing from the scope of the invention. The electrode i6 may be connected to the transformer winding directly but even in this case'an inductance is suitable. For this reason, the latter is designated by I! in the figure.

The invention is not limited to installations in which the discharge circuit is closed by means of a spark gap becoming operative. The establishment of the current may just as well be brought about in a diiferent manner, for example by supplying a suitable potential to an auxil iary electrode or by the establishment of the heating current of the incandescent cathode of the X-ray tube or of a discharge tube which may be connected in series with the latter.

What we claim is:

1. An X-ray installation comprising an X-ray tube, a high-tension transformer, a condenser, an alternating current source for said transformer, means including a rectifying device for charging said condenser from said transformer during a period comprising numerous cycles of the alternating current, and means for subsequently discharging the condenser through a discharge circuit comprising said X-ray tube and one of the windings of said transformer, said last means including a member to interrupt the discharge circuit during the charging of the condenser.

2. An X-ray installation comprising an X-ray tube having a cathode and an anode, a high-tension transformer having a primary and a secondary winding, a rectifying device and a circuit closer, said rectifying device being connected in series relation with said condenser and the secondary winding of said transformer, and said X-ray tube and circuit closer being connected in series relation with each other and connected directly across said rectifying device with the cathode of the X-ray tube corresponding to the positive terminal of the rectifying device and the anode to the negative terminal thereof.

3. An X-ray installation comprising an X-ray tube, a condenser, means including a transformer for charging said condenser, a discharge circuit for said condenser including said X-ray tube and a winding of said transformer, and a discharge circuit independent ofsaid transformer and including said X-ray tube.

ALBERT BOUWERS. ALFRED KUNTKE. 

